1. Field of the Invention
The present invention relates to a bonding agent to bond a plurality of aluminum nitride sintered bodies, an aluminum nitride composite body, and a method of manufacturing the same.
2. Description of the Related Art
Conventional methods to bond aluminum nitride sintered bodies to each other include a solid state bonding method and a solid-liquid state bonding method. In the solid state bonding method, a bonding agent is interposed between the aluminum nitride sintered bodies, and bonding is performed in a state where the bonding agent is not melted, that is, the bonding agent is solid. The solid state bonding can provide good bonding by heating at a high bonding temperature of 1850° C. or more (for example, see Patent Literature 1).
In the solid-liquid state bonding method, a bonding agent is interposed between the aluminum nitride sintered bodies, and bonding is performed in a state where part of the bonding agent is melted and solid and liquid are mixed. Some types of the solid-liquid state bonding method can provide good bonding by using a flux containing 25 to 45 wt % calcium oxide, 5 to 30 wt % yttrium oxide, and balance aluminum oxide and heating the aluminum nitride sintered bodies at a bonding temperature of 1650 to 1800° C. (for example, see Patent literatures 2 and 3).
Moreover, a heater including a heating element and an electrostatic chuck including an electrode are manufactured using the above described bonding methods. The heater and electrostatic chuck are used in a corrosive gas environment.
Patent Literature 1: Japanese Patent Laid-open Publication No. 8-73280
Patent Literature 1: Japanese Patent Laid-open Publication No. 10-167850
Patent Literature 1: Japanese Patent Laid-open Publication No. 10-273370
However, the solid state bonding method requires heating to a high temperature of 1850° C. or more in order to obtain good bonding. Moreover, in the solid-liquid state bonding method using the flux containing 25 to 45 wt % calcium oxide, 5 to 30 wt % yttrium oxide, and balance aluminum oxide, the bonding temperature can be set lower than that of the solid state bonding. However, heating to 1650 to 1800° C. is required in order to obtain good bonding. As described above, the bonding temperature is high in either conventional bonding method, therefore the aluminum nitride sintered bodies might be deformed by bonding.
Moreover, when the bonding is performed in a manufacturing process of the heater or electrostatic chuck, the heating element or electrodes might change in quality or the volume resistivity might change due to the high bonding temperature. This might result in degradation of properties including temperature uniformity of the heater and uniformity of chucking force of the electrostatic chuck.
Furthermore, the high bonding temperature increases energy required for bonding or requires processing again after bonding due to deformation, thus increasing manufacturing costs.